This Shared Instrumentation Grant proposal requests funds to purchase a high resolution, high sensitivity positron emission tomography (PET) scanner dedicated to imaging the distribution of positron-emitting radiotracers in small animals. The proposed animal PET scanner will expand and enhance basic and applied functional imaging research at the University of Pittsburgh Medical Center (UPMC). The proposed scanner, MicroPET (Concorde Microsystems, Inc.), is capable of quantitative dynamic PET imaging and can accommodate animals ranging in size from mice to the heads of rhesus monkeys. The MicroPET will be sited at the UPMC PET Facility and managed and directed by an Internal Advisory Committee made up of the co-investigators and major users cited in this proposal. The purchase of a dedicated animal PET scanner will benefit ongoing and developing functional imaging research programs at UPMC. There are three major areas in which these benefits will be realized. First, the improved spatial resolution of the MicroPET system (approximately 2.0 mm FWHM compared to approximately 4.5 mm for the current CTI/Siemens HR+ scanner) is more suitable for PET imaging of small animals, as partial volume averaging of small structures would be considerably less with the MicroPET system. Second, the MicroPET would facilitate a rapid and effective screening and evaluation of prospective radiotracers under development at the UPMC PET Facility. Use of MicroPET would make possible the acquisition of a complete kinetic profile of candidate radiotracers in each animal experiment and would obviate the need to kill animals at different stages of costly or complicated experimental protocols. In addition, the animals could be used as their own controls in serial challenge or interventional studies. Third, the MicroPET scanner will expand the role of functional imaging in basic science research, as it will allow unique research to be conduced which is impossible or too invasive to be conducted in human subjects. This research would include imaging of transgenic mice, studies of treatment efficacy in tumor-bearing animals, simultaneous PET and microdialysis experiments in rats, or studies of animal models of disease (e.g., Parkinson's disease). Thirteen different research projects that would utilize the proposed MicroPET high resolution scanner and benefit from its acquisition are described.